Fuel system



3 Sheets-Sheet 1 MHV D. J. CMI-ERQN ErAL FUEL SYSTEM Oct. 25, 1960 Filed may 1s, 1957 Ovct. 25, 1960 D. J. CAMERON ErAL 2,957,682

FUEL SYSTEM 3 Sheets-Sheet 2 Filed lay 13. 1957 INV ENTOR a/VALD IGM/15km BYUa/vfZA//PA/ w am, 62M, .r1

Oct. 25, 1960 Filed Hay 13, 1957 D. J. CAMERON ETAL FUEL SYSTEM 3 Sheets-Sheet 3 2,957,682 Patented Oct. 25, 1960 United States Patent FUEL SYSTEM This invention relates to fuel systems, and more particularly to laminar flow fuel distribution means for fuel systems adapted for use with internal combustion englnes. l

Any fuel injection system for internal combustion engines, whether it be of the intermittent or continuous ilow type, must be adapted to supply approximately forty to fty times as much fuel at maximum engine fuel requirements fas it does at minimum engine fuel requirements. For example, a given engine may require fuel a-t a rate ranging from three to one hundred and twenty pounds per hour; in the case of an eight cylinder engine, the-rate of fuel supply to each cylinder would, of course, b

one-eighth of the total rate.

In the case of turbulent ow systems, assuming a fixed jet is employed, the quantity of fuel llowed varies with the square root of the pressure. Using the above range of flow rates, the ratio of the pressure required' to flow 120# per hour to that required to llow 3# per hour is approximately 1600/1; thus if a relatively small jet size is selected so as to 4flow 120# per hour at a pressure -as high as 400 p.s.i., the pressure 'at 3# per l'lour. will be only 10" of gasoline or about 1A p.s.i., which is the minimum necessary at idle to overcome the effects of angularity.

It is thus apparent that the use of a fixed-jet, turbulent` flow system for the above range of ilow rates requires a fuel pump that is capable of delivering fuel over a wide r-ange of pressures and at a very high upperpressure limit. Another reason for this is that if the upper pressure limit is not suiciently high, the pressure at the lower flow rate will drop off to a value that is insufficient to overcome the fuel vapor pressure at idle speeds, and serious vapor problems will be experienced at or near 4 idle speeds.

While such pumps are available, they are expensive, and any fuel system requiring such a pump suffers a serious cost disadvantage. sizes required by high pressure turbulent flow systems are easily blocked by dirt particles, varnishes, etc. Also, it is diflicult to calibrate suchrsystems so that all of the cylinders are supplied with the same amount of fuel.

It is now proposed to provide a laminar flow system, wherein fuel flow varies directly with the pressure and wherein extremely small jet sizes are not required to maintain minimum flow pressures. Using the above range of ilow rates, the'ratio of the upper and lower limit pressures in the proposed system yis only 40/ 1, |and if the laminar flow restriction employed is such as to provide a low pressure system having a maximum pressure of approximately 25 p si., the pressure at the low ow rate will still be about 24" of gasoline pressure so as to substantially eliminate vapor problems at idle speeds and to completelylveliminate langularityv problems.

'Ihe proposed system will permit the use of a less expensive pump and eliminate the need for small jets which tend to foul. Even if it is desired to employ a higher pressure pump, the proposed system will provide the desired low range fuel flow rate Iat pressure suflicient to overcome vapor problems, approximately l0 p.s.i. in the case of pump operating at 400 p.s.i. at the maximum flow rate.

The proposed system comprises a low volume, constant pressure chamber supplied With metered fuel from any desired metering device, a nozzle at each intake port, and a laminar flow conduit from the constant pressure chamber to each nozzle. Each conduit comprises a length of metal tubing having a length of wire inserted therein, with the l.D. of the tubing and the O.D. of the wire being such as to provide a laminar ow path in the diametrical clearance therebetween. The tubing and the wire are commercially available, and the commercial tolerances thereof are such that the ow of fuel to the various intake ports may be easily adjusted or equalized merely by varying the length of wire as compared to the length of tubing or by suitably crimping the tubing. No jets are required at the nozzle, except a relatively large fuel directing jet and an air jet, which provides sufficient restriction -to flow of air through an atmospheric air inlet to maintain atmospheric pressure at the fuel `directing jet. i

' The proposed system is thus easily constructed fromV inexpensive, commercially available materials, and it can be calibrated very easily without expensive reworking. In addition, the conduits have a low volume so that they are fil-led more rapidly on starting.

These and other objects and advantages of the -invention will become more apparent by `reference to the fol-lowing specification and drawings, wherein:

Fi-gure l is a diagrammatic top plan view of a fuel system embodying the invention;

Figure 2 is an enlarged top plan View of one of the elements of Figure 1;

Figure 3 Vis a vertical cross-sectional view taken on the plane of line 3-3 of Figure 2 and looking in the direction of the arrows;

Figure 4 is a Ver-tical cross-sectional view taken on the plane of line 4--4 of Figure 2 and looking in the Furthermore, the small jet direction of the arrows;

Figure 5 is an enlarged top plan view of another element shown by Figure l;

` Figure 6 is a vertical cross-sectional view taken on the plane of line `6-6 of Figure 5 and looking in the direction ofthe arrows;

Figure 7 is an enlarged fragmentary view, partly cut away and in cross-section, illustrating in greater detail the construction of one of the conduits shown by Figure l;

Figure 8 Iis a graph comparing fuel ilow versus pressure curves for a fixed-jet, turbulent llow system and a fixed-jet, laminar ilow system embodying the invention.

'Referring to the drawings in greater detail, Figure 1 illustrates a fuel system 10 embodying the invention and tted on an internal combustion engine 12 having an intake manifold 14 with a plurality of intake ports 16.

The engine 12 isv provided with any suitable combustion air control device 18, the details of construction of which are not important to the invention except that it may embody a starting fuel system which will be referred to later, and a fuel system 10 including a fuel tank 20, a fuel pump 22, a fuel metering device 24, and `a fuel distribution system embodying the invention and generally designated by the numeral 26. The parscribed, and the pump 22 is that of which the pressure range and upper pressure limit may be reduced by use of the invention, las described above.

In the system shown by Figure l, unmetered fuel is supplied by the pump 22 from the tank 20 to the metering unit 24 by means of the conduit 28, and metered fuel is supplied through the conduit 30 rto the header 32; from the header 32, mete-red fuel under a constant pressure is supplied through the individual conduits 36 to the individual inlet ports i6, each of which is provided with a nozzle assembly 34.

The header 26 shown in greater detail by Figures 2, 3 and 4 may comprise a lower portion 38 having an annular recess 40 formed therein and an upper portion 42 formed to provide an annular recess 44 and a constant pressure manifold chamber 46 connected with the recess 44 by means of the passage 48 having an enlarged portion 50 adapted to receive an annular valve seat 52. The upper and lower portions 42 and 38 may be secured together by any suitable means such as bolts 54, with the flexible diaphragm 56 being held between the upper and lower portions 42 and 38 and serving as a gasket. The diaphragm 56 has secured to the center portion thereof in any suitable manner a valve 58 adapted to engage the valve seat 52, with the valve 58 preferably being cone-,shaped so as to provide a self centering valve as'- sembly.

With the above or any equivalent construction, a lower chamber 60 of which the diaphragm forms one wall is provided; the chamber 60 is vented to atmosphere by means of the passage 62 so as to permit free movement of the diaphragm 56. The upper chamber 64 on the opposite side of the flexible diaphragm 56 has a metered fuel inlet 66; when the metered fuel pressure ex- Ceeds the force of the spring 68 positioned between the diaphragm cup 70 and the shoulder 72, the valve 58 is opened and metered fuel may pass into the constant pressure chamber 46 to he distributed to the eight individual fuel outlet passages 74 communicating with the constant pressure manifold chamber 46.

As shown in detail by Figures and 6, there is provided at each inlet port 16 what may be termed a nozzle assembly 34, including a body 76 having a portion 78 adapted to be threaded into the wall of the inlet passage 16. The body 76 may be formed to provide a passage 80 extending in the general direction of the path of the inlet port, with the passage 80 being threaded at its upper portion 82 and terminating at the inlet port end thereof in a conical or reduced diameter portion 84 communicating with the inlet port through a restriction 86. A second threaded passage 88 may be provided adjacent the threaded portion 82 of passage 80, and any suitable air lter device 90 may be threaded therein. A third horizontal passage 92 provides communication between the end of threaded passage 88 and the passage 80, with the outer end of the passage 92 being blocked olf. With this or an equivalent construction, manifold vacuum in the inlet port will cause clean air to be drawn through the filter device 90 and eventually through the restriction 86. The restriction 86 is preferably of such size as to maintain substantially atmospheric pressure, rather than engine intake manifold pressure, at the conical portion 84 of passage 80.

Referring again to Figures 5 and 6, the nozzle assembly 34 also includes a conduit retaining member 94 having threaded portions 96 and 98 separated by a hexagonal or other nut member l100 and a tubular portion 102 necking down to a relatively large fuel directing jet 104. The end of the fuel directing jet 104 is spaced from the walls of the conical portion 84 of the passage 80 a sufficient distance so as not to constitute a pressure reducing venturi or restriction which would prevent the objective of maintaining atmospheric pressure at the end of the fuel directing jet 104.

It is now apparent that the fuel directing jet 1,04 is not the equivalentY of the fixed jet in a yhigh pressure, turbulent ow system; on the contrary, its only purpose is to direct the stream of fuel through the restriction 86, the size of which is determined by its function of preventing engine manifold vacuum from acting on the fuel at the jet 104. The member l94 is, of course, threaded into the body 76 so that the tubular portion 102 is positioned co-axially within the passage to provide a clearance 106 through which clean air may pass for the above purpose.

Extending between each of the nozzle asemblies 34 and one of the laterally extending passages 74 in the header 32, is a laminar flow conduit 36 consisting of suitable lengths of commercially available metal tubing 106 and stainless steel or other wire 108, with the inner diameter of the tubing and the outer diameter of the wire being such as to provide a diametrical clearance 109 therebetween constituting a laminar flow path or restriction through which metered fuel from the constant pressure chamber may flow to the fuel directing jet 104, through the restriction 86 and into the intake ports 16. This construction is shown in greater detail by Figure 7.

It is deemed advisable at this point to derive some of the relationships existing in flow through a cylindrical ow path such as that provided by a plain tube and through an annular flow path provided by applicants tube with a solid insert. For this purpose, the following symbols will be employed and values assumed:

r=kinematie viscosity for gasoline at about 70 F.:

7.32 10* ftf/sec.

lalength of ow path in feet g=acceleration due to gravity=32.2 ft. /sec.2

D=diameter of plain tube in ft.

d1rDm d R4"'21rDm2 With the exception of the derivation specifically explained, the following basic relationships are known and can be found in most text books relating to fluid mechanics:

Plain tube fiow pat/1 c@ Q h D29 (any flow) NR- T 64 f= (laminar flow) Q VA Annular flow path wir For a plain tube, V is the average velocity across a parabolic front. For two-dimensional flow between plates, the shape of the velocity front is a parabola in one view and a rectangle in the other view. The average velocity for two-dimensional flow is 3/2 that of tube flow. Thus, when the maximum peak velocity is the same, 3/2Vp=V1 or Vp=2/3V1, therefore 'From the above basic relationships, the following relatlonships can be derived by simple substitutions, etc.:

Plain tube flow path It is thus apparent that given a Qmx, in Equation 1 will give a particular set value for D, which when used in Equation 2 will give a particular set value for l; that is, D appears in both equations and cannot be changed in (2) without affecting Qm,x in (1). In other words, to decrease l in (l2) requires a decrease in D, which requires an increase in NR in (1); the latter cannot be done Without getting into turbulent ilow, if NR was already selected close to 2000 for laminar ow.

Solving the above equations for D and l, where the other values are those given in the above list of symbols, gives the following set values: D=.0081 ft. and l=47.5 ft. This means that to provide the above referred to benefits of a laminar ilow system in an engine requiring 120# of fuel per hour, the plain tube conduits to the nozzle must each be approximately .1 inch in diameter and at least 47.5 ft. long. This is obviously not a practical design, since an eight cylinder system would require 380 ft. of conduit. Furthermore, each line has a volume of 4.48 cub. in. (total volume=35.84 cub. in.), which presents a vapor problem and requires a long starting time if the lines should be empty and idle ilow rate is Sii/hr.

Annular flow path It is apparent from Equation 1 above that given Qmx, Dm is set for a given NR; if Dm needs to be increased, however, NR can be decreased from the critical 2000 value, getting even further from the turbulent ow range. In other words, Dm is flexible to a minimum. In Equation 2, l is a function of d3; therefore, any suitable combination of l and d can be used and laminar ow will still prevail. Since l does not appear in Equation 1, any values of can be used in Equation 2 without affecting Qmm in Equation 1.

Again, assuming the values given in the list of symbols, actual sets of values of l and Dm were found to be as follows, Where d=.008 inch:

n1:.041 inch (min. since NR=200.0) and l=.474 ft. m=.l25 inch (NR=516) and l=1.74 ft.

Using the latter combination, each line has a volume of only .0768 cub. in. (total volume=.6144 cub. in.), greatly reducing vapor problems and starting time.

The conduits 36 are made very simply by cutting oif a suitable length of tubing 106 and inserting an equal length of wire 108 into the tubing so that the free ends thereof match. The effective laminar ow restriction is dependent upon the diametrical clearance 109 between the wire 108 and the tubing 106 and upon the length of wire in the tubing. It `can thus be seen that the clearance 109 and the length of wire may be varied as desired. No particular means is required to retain the wire in the tubing, since it will be retained by friction, particularly when the conduits are bent as shown in Figure '1.' One end of each such conduit assembly 36 may then be inserted into the outer end of each of the laterally extendingvpassages 74 and soldered or otherwise secured to the header. The other end of each of the conduit assemblies 36 is merely inserted into the passage 110-ex tending through the member 94 until the free end of the tubing engages the necked down portion of the tubular portion 102. A retaining ring 112 may be soldered or otherwise secured to the tubing 106 and a suitable nut 114 may be threaded on the threaded free end 98 of the member 94 to secure the appropriate conduit 36 to its nozzle assembly 34. p

It has been stated above that the air control device 18 may incorporate a starting fuel system. In that event, a conduit 116 for by-passing metered fuel from the chamber 64 to the tank 20 is provided. In addition, a conduit -118 extending from the pump outlet conduit 28, through any suitable starting fuel device represented generally by the numeral 1-20 and to the inlet 122 is also provided. In addition, the control device 118 and the starting fuel device 120 are provided with suitable means to by-pass metered fuel back to the tank 20 and to supply starting fuel to chamber 46 on starting and to cut off start fuel and close line 116 when the engine has started.

In the particular embodiment of the invention shown and described above, metered fuel from the metering unit 24 is supplied to the chamber 64 in the header 32. On starting the engine, the conduit 116 will be open, and metered fuel will be by-passed to the tank 20, since spring 68 will keep the valve 58 closed. At the same time, starting fuel in the proper amount, as controlled by the start fuel device 120, will be supplied to the chamber 46, from which it will be distributed to the inlet ports 16. As soon as the engine starts, the start fuel will be cut off, the line 116 will be closed and metered fuel pressure will be increased in chamber 64. When the metered fuel pressure exceeds and force of the spring 68, the valve 58 will open and metered fuel will enter the constant pressure manifold chamber 46 and be distributed to the separate conduits 16, as already described.

While a start fuel device 120 is shown and described, it is to be understood that the principal feature of the invention, the laminar flow fuel distribution sys-tem, does not necessarily require the use of a start fuel device.

The diametrical clearance 109 between the tubing 106 and the wire 108 of each conduit assembly 36 provides a laminar flow restriction for the fuel so that fuel flow varies directly with pressure instead of as the square root of the pressure, as it would in the case of a fixed-jet, turbulent flow system.

Y The above is illustrated by Figure 8, wherein .the curve A represents Fuel Flow versus Fuel Pressure for a fuel system embodying the invention and curve B illustrates the same for a turbulent flow, fixed-jet system. These curves are intended to be qualitative, rather than quantitative, in nature, since the exact curves would require the specification of actual fixed-jet and restriction dimensions, pump capacities, etc. However, it will be noted generally that the system disclosed herein will supply of total fuel per hour through eight laminar flow restrictions at a maximum pressure of 25# per square inch Where each restriction has an area of approximately .0057 sq. in. for the same flow through eight lfixed-jets, each having an area of .000056 sq. in., the turbulent ow system will require a maximum pressure of 200# per square inch. At the low flow ranges, however, the pressure in the turbulent system would drop below that of the system embodying the invention and below the minimum required to overcome angularity and vapor formation, unless the small jet size is used.

It is to be observed that the above advantages of the invention are .accomplished with a laminar flow restriction having nearly 100 times the area of the fixed jet in an equivalent turbulent ilow system. Thus, the laminar ow restrictions are that much less likely to foul.

The laminar iiow restrictions of each conduit may be easily calibrated to equalize or vary the liiow to each cylinder simply by varying the length of wire or by suit ably crimping the tubing in one or more places. This may be done by any mechanic whenever it becomes necessary, such as when one or more conduits are replaced and the fuel flow therethrough must be matched with the other original conduits, etc.

It is also apparent that the lconduits are extremely simple in manufacture from inexpensive commercially available materials, the commercial tolerances of which are such that the above described means Iof calibration is suflicient.

The conduits, particularly where the wire and tube lengths are substantially equal, have a very low volume so that the system is quickly filled with fuel on starting. In addition, the low volume aids in reducing vapor problems.

While but a single modification of the invention is shown and certain dimensions are indicated for purposes of illustration, it is apparent that other modifications thereof may be made and any suitable dimensions may be employed without exceeding the scope of the invention as set forth in the appended claims.`

What we claim is:

l. A fuel distribution system for an internal combust-ion engine, said system comprising a plurality of conduits, each of said conduits comprising a suitable length of tubing having a suitable length of wire inserted therein, said conduits being adapted by reason of the diameterical relation between said tubing and said wire to supply substantially all of the fuel required by said engine by laminar flow of said fuel.

2. In a port injection fuel system for an internal combustion engine having a plurality of intake ports, means wherein fuel flow varies as a linear function of the fuel pressure over substantially the entire range of engine requirements for distributing metered fuel to each of said ports, said means including a laminar flow conduit leading to each of said ports, each of said conduits comprising a length of tubing having a suitable length of solid rod inserted therein, with the diametrical clearance between said tubing and said rod being such as to provide a laminar flow path for said metered fuel.

3. A fuel system for an internal combustion engine requiring fuel at a maximum rate of about l2() #/hr. and having a plurality of intake ports, comprising a fuel tank, a fuel pump rated at 50 p.s.i. or less, fuel metering means and metered fuel distributing means, said fuel distributing means including a nozzle at each of said intake ports, a constant pressure metered fuel chamber posterior to said metering means and a laminar flow conduit between said chamber and each of said nozzles,

each of said conduits comprising a length of tubing having a length of wire inserted therein, with the diametrical clearance between said wire and said tubing being such as to provide laminar flow `of said metered 4fuel for all engine fuel requirements.

4. In `a fuel system for an internal combustion engine having an intake manifold with a plurality of intake ports, a nozzle for admitting fuel to each of said inlet ports, said nozzle comprising a body having an atmospheric air inlet 4terminating in a restriction and a hollow member disposed with clearance in said air inlet and terminating in a low restriction fuel directing jet, said fuel directing jet being positioned sufficiently back from said restriction to maintain atmospheric pressure at said fuel directing jet, and a laminar llow fuel conduit leading to said fuel directing jet, said conduit comprising a tube having a wire inserted therein, the relation of the O.D. of said wire and the LD. of said tube being such that a laminar fuel ow path is provided by the diametrical clearance therebetween for all engine fuel requirements, the relation of the areas of said diametrical clearance and said fuel directing jet being such that the function of said fuel directing jet is primarily to direct the fuel stream through said restriction and not to restrict fuel flow.

5. In a fuel system for an internal combustion engine having an intake manifold with a plurality of intake ports, a nozzle for admitting fuel to each of said inlet ports, said nozzle comprising a body having ian atmospheric air inlet terminating in a restriction communicating with said inlet port and of maximum size that will maintain atmospheric pressure in said nozzle, a hollow member disposed with clearance in said air inlet and terminating in a low restriction fuel jet to direct fuel through said restriction, said fuel jet being positioned sufficiently away from said restriction so as not to reduce the pressure at said fuel directing jet below atmospheric pressure, and a fuel conduit leading to said fuel jet, said conduit comprising a tube having a -wire inserted therein, the relation of the O D. of said wire and the I.D. of said tube being such that a laminar fuel flow path is provided by the diametrical clearance therebetween for all engine fuel requirements, the areas of said diametrical clearance on said fuel directing jet being such that the function of said fuel directing jet is primarily to direct the fuel stream and not to' restrict fuel flow.

References Cited in the file of this patent UNITED STATES PATENTS 662,296 Palmer Nov. 20, 1900 2,406,141 Fredericks Aug. 20, 1946 2,478,613 Weber Aug. 9, 1949 2,511,213 Leslie June 13, 1950 

